Pollutionwatch: December often a peak month for winter smog

December is often a peak month for winter smog. Over 60% of the most serious UK smogs since 1873 have been in December. During December 2012, high pressure centred over Iceland led to settled weather over Northern Ireland on the 10th causing air pollution to reach the top level of 10 on the Government's air quality index. Natural gas has only been available in Northern Ireland since the late 1990s and is still to reach many towns meaning that wintertime air pollution here is dominated by smoke from coal fires and heating oil emissions.

On the 11th settled weather moved eastwards and pollution problems spread to Glasgow. A further shift in the focus of the high pressure system on the 12th and 13th caused polluted air from France and Belgium to drift over the southern part of the UK. The arrival of this continental air was seen at Harwell in rural Oxfordshire where air pollution concentrations quadrupled in a 10 hour period. The combination of polluted continental air and exhaust from traffic led to pollution problems across London, south-east England and Birmingham. Further north, parts of Yorkshire, Preston and Wigan experienced pollution from other cities in the UK.

The remainder of the month was dominated by wet Atlantic weather. This brought flooding problems to many areas but it ensured rapid dispersion of air pollution from our cities. Unsettled weather also prevented pollution problems from New Year's Eve fireworks.